Drive mechanism for a bicycle transmission assist mechanism

ABSTRACT

A drive mechanism for a bicycle transmission assist mechanism includes a crank arm having a drive member. The drive member includes a first abutment facing a forward rotational direction of the crank arm and a non-concave sloped surface facing a rearward rotational direction of the crank arm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/474,916,filed Dec. 29, 1999 now U.S. Pat. No. 6,860,171.

BACKGROUND OF THE INVENTION

The present invention is directed to control devices for bicycletransmissions and, more particularly, to an apparatus that usesrotational power from a rotating crank, axle or some other member toassist the operation of the bicycle transmission.

A typical bicycle transmission is operated by a shift operating wireconnected between the transmission and a manually operated shiftoperating device mounted on the handlebar. The rider operates the shiftoperating device to selectively pull or release the shift operating wirewhich, in turn, operates the transmission in the desired manner.

One of the goals of bicycle transmission design is to make thetransmission easy to operate with a minimum amount of effort. Thisinvolves minimizing the force needed to operate the shift operatingdevice as well as minimizing the amount of unnecessary movement of theshift operating device. In the case of bicycle transmissions such asderailleurs which are used to shift a chain from one sprocket toanother, the amount of force needed to derail the chain from onesprocket and move it to another can be quite large, especially when thedestination sprocket is substantially larger than the originatingsprocket and the rider is exerting substantial pedaling force on thechain. The necessary operating force can be reduced by operating theshift operating device when only a small pedaling force is being appliedto the chain, but that requires the rider to consciously alter his orher pedaling technique and/or consciously operate the shift operatingdevice only when a small pedaling force is being applied to the chain.That can be very distracting, especially in a racing environment. Also,the actuation ratio of some derailleurs may be somewhat large.Consequently, the shift operating wire must move a substantial distanceto fully move the chain from one sprocket to another, thus requiring therider to move the shift operating device by a correspondingly largeamount.

SUMMARY OF THE INVENTION

The present invention is directed to an assist device for shifting abicycle transmission wherein very little force is needed to operate thetransmission, the shift operating wire needs to be pulled or releasedonly by a very small amount, and the assist device automaticallydetermines when to perform the shifting operation. More specifically,the present invention is directed to a drive mechanism that operatessuch an assist device.

In one embodiment of the present invention, a drive mechanism for abicycle transmission assist mechanism includes a crank arm having acrank axle mounting hole and a drive member. The drive member includes afirst abutment facing a forward rotational direction of the crank armand a non-concave sloped surface facing a rearward rotational directionof the crank arm.

In a more specific embodiment, the drive member comprises an annulardrive ring mounted coaxial with the crank axle mounting hole. The firstabutment is substantially perpendicular to an outer peripheral surfaceof the crank arm, and the first sloped surface has an arcuate shape.Preferably, the outer peripheral surface of the drive ring at thelocation of intersection with the abutment extends at a constant radiusof curvature for more than 20°.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross sectional view of a bicycle bottom bracketassembly that incorporates a particular embodiment of an assistingapparatus according to the present invention for shifting a bicycletransmission;

FIG. 2A is an oblique view of a particular embodiment of a right sidecrank arm assembly according to the present invention;

FIG. 2B is an oblique view of an alternative embodiment of a right sidecrank arm assembly according to the present invention;

FIG. 3 is an oblique view of an alternative embodiment of a left sidecrank arm assembly according to the present invention;

FIG. 4 is an oblique view of a particular embodiment of an assistingapparatus according to the present invention;

FIG. 5 is a side view of the assisting apparatus of FIG. 4 in an idlestate;

FIG. 6 is a side view of the assisting apparatus of FIG. 4 when anoperating wire is moved a first time;

FIG. 7 is a side view of the assisting apparatus of FIG. 4 showing aderailleur positioning cam rotating with the rotating member for pullinga derailleur actuating wire;

FIG. 8 is a side view of the assisting apparatus of FIG. 4 just prior todisengaging the derailleur positioning cam from the rotating member;

FIG. 9 is a side view of the assisting apparatus of FIG. 4 showing thedisengagement of the derailleur positioning cam from the rotatingmember;

FIG. 10 is a side view of the assisting apparatus of FIG. 4 when theassisting apparatus has completed the shifting operation;

FIG. 11 is a side view of the assisting apparatus of FIG. 4 when theoperating wire is moved a second time;

FIG. 12 is a side view of the assisting apparatus of FIG. 4 showing thederailleur positioning cam rotating with the rotating member forreleasing the derailleur actuating wire;

FIG. 13 is an oblique view of a bicycle bottom bracket assembly thatincorporates another embodiment of an assisting apparatus according tothe present invention for shifting a bicycle transmission;

FIG. 14 is an oblique view of the assisting apparatus shown in FIG. 13with the derailleur and crank arm removed;

FIG. 15A is a side view of the mounting member used with the assistingapparatus shown in FIG. 13 illustrating the configuration of controlsurfaces;

FIG. 15B is a view taken along line 16B-16B in FIG. 15A;

FIG. 16 is a side view of the assisting apparatus shown in FIG. 13 in anidle state;

FIG. 17 is a side view of the assisting apparatus shown in FIG. 13 whenan operating wire is moved in a first direction;

FIG. 18 is a side view of the assisting apparatus of FIG. 13 showing thederailleur positioning cam rotating with the rotating member for pullingthe derailleur actuating wire;

FIG. 19 is a side view of the assisting apparatus of FIG. 13 when theassisting apparatus has completed the shifting operation;

FIG. 20 is a side view of the assisting apparatus shown in FIG. 13 whenan operating wire is moved in a second direction;

FIG. 21 is a side view of the assisting apparatus of FIG. 13 showing thederailleur positioning cam rotating with the rotating member forreleasing the derailleur actuating wire;

FIG. 22 is a partial cross sectional view of a bicycle bottom bracketassembly that incorporates an alternative embodiment of an assistingapparatus according to the present invention for shifting a bicycletransmission;

FIG. 23 is a side view of a particular embodiment of a right side crankarm assembly used with the assisting apparatus shown in FIG. 22;

FIG. 24 is a more detailed view of the drive member shown in FIG. 23;and

FIG. 25 is a more detailed view illustrating the shape of the sealingmember shown in FIG. 23.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a partial cross sectional view of a bicycle bottom bracketassembly 10 that incorporates a particular embodiment of an assistingapparatus 14 according to the present invention for shifting a bicycletransmission. Bottom bracket assembly 10 includes a bottom bracket shell18 that is mounted to a typical bicycle frame (not shown), a tubularaxle supporting sleeve 22, a sleeve coupler 26, an axle 30, ballbearings 34 and 38, and crank arm assemblies 42 and 46. Axle supportingsleeve 22 has a radially outwardly extending flange 50 on a first endthereof for retaining a mounting member 300 of assisting apparatus 14 tobottom bracket shell 18, bearing surfaces 58 and 62 for engaging ballbearings 34 and 38, respectively, and an outer peripheral surface 66 ata second end for engaging an inner peripheral surface 70 of sleevecoupler 26. Sleeve coupler 26 includes a radially outwardly extendingflange 74 for engaging the side of bottom bracket shell 18.

In this embodiment, axle 30 is a substantially hollow tubular memberhaving bearing surfaces 78 and 82 for engaging ball bearings 34 and 38,respectively, splines 86 and 90 for engaging complementary splines 94and 98 formed on the inner peripheral surfaces of the crank axlemounting holes 99 and 100 in crank arm assemblies 42 and 46,respectively, and threaded inner peripheral surfaces 102 and 104 forengaging threaded bolts 108 and 112, respectively, that mount crank armassemblies 42 and 46 to axle 30. Thus, axle 30 and crank arm assemblies42 and 46 are rotatably supported within bottom bracket shell 18 by ballbearings 34 and 38.

As shown in FIGS. 1 and 2A, crank arm assembly 46 includes an elongatedcrank arm body 120, a crank axle mounting boss 124 at the first endhaving an inner peripheral surface defining the crank axle mounting hole100 and splines 98, and a threaded pedal mounting hole 128 on the secondend. A plurality of, e.g., five sprocket mounting members 132 extendradially outwardly from a seal-supporting boss 133 mounted around crankaxle mounting boss 124. Seal supporting boss 133 has an annular groove134 for supporting a ring seal 135 which sealingly engages an outersurface of a side cover 137 of assisting apparatus 14.

In this embodiment, a generally ring-shaped large diameter sprocket 136with a plurality of radially outwardly projecting teeth 138 and an innerperipheral surface 140 is formed as one-piece with the plurality ofsprocket mounting members 132. A generally ring-shaped small diametersprocket 144 with a plurality of radially outwardly projecting teeth 148and an inner peripheral surface 152 is mounted to the plurality ofsprocket mounting members 132 through bolts 156 and spacers 160. Anannular drive ring 170 coaxial with crank axle mounting hole 100 has aplurality of splines 174 formed on an inner peripheral surface thereoffor nonrotatably engaging complementary splines 178 on the outerperipheral surface of crank axle mounting boss 124 laterally inwardly ofseal supporting boss 133. Each spline 174 has a first circumferentialside 180, a second circumferential side 182, and a radially innermostside 184 bridging the radially innermost ends of first circumferentialside 180 and second circumferential side 182. In this embodiment, firstcircumferential side 180 and second circumferential side 182 each areflat and perpendicular to the direction of rotation of crank armassembly 46. Splines 178 on crank axle mounting boss 124 have the samestructure. Of course, other shapes and orientations are possible for thesplines. Also, drive ring 170 could be formed one-piece with the crankaxle mounting boss 124.

The outer peripheral surface of drive ring 170 forms a pair of driveprojections 190A and 190B, each having an abutment 192A and 192B,respectively, disposed 180° from each other and facing in the forwarddirection of rotation of crank arm assembly 46. In other words,abutments 192A and 192B face in the counterclockwise direction in FIG.2A.

Abutments 192A and 192B follow an imaginary straight line extendingradially outwardly from the axis of rotation X of crank arm assembly 46and perpendicular to the outer peripheral surface of crank axle mountingboss 124. The outer peripheral surface of drive ring 170 at the locationof intersection with abutments 192A and 192B extends counterclockwise inFIG. 2A at a constant radius of curvature for more than 20° and, in thisembodiment, more than 45° until it nears the rear of the following driveprojection, whereupon the radius of curvature increases in a nonconcavemanner to the tip of the projection. In this embodiment, the outerperipheral surface of drive ring 170 forms a flat ramp up to the tip ofthe corresponding projection, but it could be arcuate as well. As seenclearly in FIG. 2A, drive projections 190A and 190B extend only slightlyfrom the outer peripheral surface of drive ring 170. Drive projections190A and 190B clearly have a diameter less than the diameter of innerperipheral surface 152 of small sprocket 144 as well as the diameter ofannular seal groove 134.

The crank arm assembly 46 shown in FIG. 2A has the abutments 192A and192B oriented generally transverse to a longitudinal median (crank arm)axis R of the crank arm body 120. However, the location of abutments192A and 192B may be placed in other locations according to the designof the sprockets or for other considerations. For example, FIG. 2B is aside view of an alternative embodiment of a crank arm assembly 46′according to the present invention. This embodiment also has anelongated crank arm body 120, crank axle mounting hole 100, splines 98and a threaded pedal mounting hole 128. However, in this embodiment adrive ring 170′ has a smooth inner peripheral surface 171′ that ispress-fit onto the outer peripheral surface 123 of a crank arm boss124′. As with the embodiment shown in FIG. 2A, abutments 192A and 192Bfollow an imaginary straight line extending radially outwardly from theaxis of rotation X of crank arm assembly 46 and perpendicular to theouter peripheral surface of crank axle mounting boss (not shown), whichhas the same shape as crank axle mounting boss 124 in FIG. 1. However,in this embodiment abutments 192A and 192B extend in a directionparallel to the longitudinal median axis R of crank arm body 120. Thisallows the abutments to initiate the operation of assist mechanism 14(described below) when the pedal is at the top or bottom of the pedalstroke.

In this embodiment, four sprocket mounting members 132′ extend radiallyoutwardly from crank axle mounting boss 124′. A generally ring-shapedlarge diameter sprocket 136 with a plurality of radially outwardlyprojecting teeth 138 and an inner peripheral surface 140 is formed asone-piece with the plurality of sprocket mounting members 132′. Agenerally ring-shaped small diameter sprocket 144 with a plurality ofradially outwardly projecting teeth 148 and an inner peripheral surface152 is mounted to the plurality of sprocket mounting members 132′through bolts 156 and spacers (not shown) in the same manner as theembodiment shown in FIG. 2A. However, in this embodiment, upshiftingchain supporting members 201A-201H are disposed on the side 203 of largediameter sprocket 136 facing small diameter sprocket 144 to lift andguide the chain (not shown) from small diameter sprocket 144 to largediameter sprocket 136. Such chain supporting members 201A-201H are wellknown, and they may comprise conical members with an inclined surfacefacing side 203 of large diameter sprocket 136, they may simply comprisecylindrical members protruding from the side 203 of large diametersprocket 136, or they may comprise some other supporting hook orabutment.

In this embodiment, chain supporting member 201A is located above thethird tooth 148 of small diameter sprocket 144 clockwise from the bottomtooth 148B aligned with the longitudinal median axis R; chain supportingmember 201B is located above and aligned between the fourth and fifthteeth 148 clockwise from bottom tooth 148B; chain supporting member 201Cis located above the sixth tooth 148 clockwise from bottom tooth 148B;and chain supporting member 201D is located above and aligned betweenthe seventh and eighth tooth 148 clockwise from bottom tooth 148B.Similarly, chain supporting member 201E is located above the third tooth148 clockwise from the top tooth 148T aligned with the longitudinalmedian axis R; chain supporting member 201F is located above and alignedbetween the fourth and fifth teeth 148 clockwise from top tooth 148T;chain supporting member 201G is located above the sixth tooth 148clockwise from top tooth 148T; and chain supporting member 201H islocated above and aligned between the seventh and eighth tooth 148clockwise from top tooth 148T.

Finally, downshift facilitating teeth 203D-203F may be formed on largediameter sprocket 136 to guide the chain onto the smaller diametersprocket 144 during a downshifting operation. Such downshiftfacilitating teeth also are well known and may comprise teeth with aside surface inclined and facing the small diameter sprocket 144, teethrotated relative to the plane of the large diameter sprocket 136, teethwith truncated tops (such as teeth 203A and 203F) and overall smallerteeth commonly called nubs or spurs. In this embodiment downshiftfacilitating teeth 203A and 203B are disposed on opposite sides oflongitudinal median axis R at the bottom of large diameter sprocket 136,and downshift facilitating tooth 203C is disposed immediatelycounterclockwise of downshift facilitating tooth 203B. Similarly,downshift facilitating teeth 203D and 203E are disposed on oppositesides of longitudinal median axis R at the top of large diametersprocket 136, and downshift facilitating tooth 203F is disposedimmediately counterclockwise of downshift facilitating tooth 203E.

As shown in FIG. 1, left side crank arm assembly 42 includes anelongated crank arm body 220, a crank axle mounting boss 224 at thefirst end having an inner peripheral surface defining the crank axlemounting hole 99 and splines 86, and a threaded pedal mounting hole 228on the second end.

Although in this embodiment the assisting apparatus 14 is located on theright side of bottom bracket shell 18, in other embodiments theassisting apparatus 14 may be located on the left side of bottom bracketshell 18. In that case, left side crank arm assembly 42 may beconstructed as shown in FIG. 3. In that embodiment an annular drive ring270 has a plurality of splines 274 formed on an inner peripheral surfacethereof for nonrotatably engaging complementary splines 278 on thelaterally innermost outer peripheral surface of crank axle mounting boss224. The structure of crank axle mounting boss 224 and drive ring 270typically but not necessarily would be the same as crank axle mountingboss 124 and drive ring 170 for right crank arm assembly 46.Furthermore, in this case the diameter of projections 290A and 290Bwould be not greater than, and preferably less than, an outer diameterof crank arm mounting boss 224 transverse to the longitudinal medianaxis L of crank arm 220.

FIG. 4 is an oblique view of a particular embodiment of an assistingapparatus 14′ according to the present invention. This assistingapparatus 14′ is structured the same as assisting apparatus 14 shown inFIG. 1 except it is intended to be mounted on the left side of thebicycle and cooperates with a drive ring 270′ which may have the samestructure as drive ring 270 shown in FIG. 3, but in FIG. 4 drive ring270′ has a smooth circular inner peripheral surface 271′ that can bepress-fit onto crank axle 30 as shown in FIG. 5 to facilitate theexplanation of the operation of assisting apparatus 14′. In any event,assisting apparatus 14′ includes mounting member 300′; a cam member(derailleur positioning cam) 304 with a cam surface 308 coupled tomounting member 300′ for rotation around a cam axis Y (which is usuallybut not necessarily coincident with rotational axis X of crank armassembly 42); a cam follower 311 cooperating with cam surface 308 formoving in response to rotation of cam member 304; a transmissionactuating element coupling member 316 for communicating movement of camfollower 311 to a transmission actuating element 320; a first couplingmember 324 coupled for rotation of cam member 304, wherein firstcoupling member 324 moves between a first engaged position and a firstdisengaged position; a second coupling member 326 coupled for rotationof cam member 304, wherein second coupling member 326 moves between asecond engaged position and a second disengaged position; and anoperating member 323 for moving first coupling member 324 to the firstengaged position.

In this embodiment, cam follower 311 includes a cam follower lever 312,wherein an intermediate portion of cam follower lever 312 is pivotablymounted to mounting member 300′ through a pivot shaft 330. A first endof cam follower lever 312 includes a roller 334 for engaging cam surface308, and a second end of cam follower lever 312 contains thetransmission actuating element coupling member 316. Transmissionactuating element 320 comprises a Bowden cable wherein a transmissionactuating wire 340 slides within an outer casing 344. Consequently,transmission actuating element coupling member 316 has the form of awire connector, wherein a wire fastening screw 350 screws into thesecond end of cam follower lever 312. Mounting member 300′ has atransmission actuating element coupling arm 354 for terminating theouter casing 344 of transmission actuating element 320 in a knownmanner. For example, transmission actuating element coupling arm 354 mayhave a threaded opening 358 (FIG. 5) for engaging a threaded portion 359of an adjustment barrel 360 used to terminate outer casing 344 and toadjust the position of outer casing 344 relative to transmissionactuating wire 340.

As shown more clearly in FIG. 7, which shows cam member 304 rotatedcounterclockwise relative to the position shown in FIG. 4, firstcoupling member 324 comprises a first pawl 370 and a first pawl mountingmember 374. A first end of first pawl 370 is pivotably connected tofirst pawl mounting member 374 through a first pivot shaft 378, and asecond end of first pawl 370 has a radially inwardly extending firstpawl tooth 382. First pawl mounting member 374 is fixed to cam member304 by a screw 386. A first biasing mechanism in the form of a firstleaf spring 388 has a first end 390 fixed to cam member 304 and a secondend 394 abutting against a first pawl control abutment 398 disposed atthe second end of first pawl 370. First leaf spring 388 biases firstpawl tooth 382 radially inwardly to the first engaged position whereinfirst pawl 370 engages either abutment 292A or 292B on drive ring 270′as discussed below.

Similarly, second coupling member 326 comprises a second pawl 400 and asecond pawl mounting member 404. A first end of second pawl 400 ispivotably connected to second pawl mounting member 404 through a secondpivot shaft 408, and a second end of second pawl 400 has a radiallyinwardly extending second pawl tooth 412. Second pawl mounting member404 is fixed to cam member 304 by a screw 416. A second biasingmechanism in the form of a second leaf spring 418 has a first end 422fixed to cam member 304 and a second end 424 abutting against a secondpawl control abutment 428 disposed at the second end of second pawl 400.Second leaf spring 418 biases second pawl tooth 412 radially inwardly tothe second engaged position wherein second pawl 400 engages eitherabutment 292A or 292B on drive ring 270′ as discussed below.

In this embodiment, operating member 323 has the shape of an operatinglever 325, wherein an intermediate portion of operating lever 325 ispivotably mounted to mounting member 300′ through a pivot shaft 450 forpivoting around an operating lever axis Z. A first end of operatinglever 325 has the shape of a hook with a control surface 454 forsupporting either first pawl control abutment 398 of first pawl 370 orsecond pawl control abutment 428 of second pawl 400 as described morefully below. A second end of operating lever 325 contains an operatingelement coupling member 458. In this embodiment, an operating element inthe form of an operating wire 460 is coupled between a shift operatingdevice mounted to the bicycle handlebar (not shown) and operatingelement coupling member 458.

Thus, operating element coupling member 458 has the form of a wireconnector, wherein a wire fastening screw 470 screws into the second endof operating lever 325. An operating member biasing spring 474 isconnected between mounting member 300′ and operating lever 325 forbiasing operating lever 325 counterclockwise.

Finally, mounting member 300′ includes pawl decoupling ramps 476 and 480for moving first pawl 370 and second pawl 400 radially outwardly intothe first disengaged position and into the second disengaged position todisengage first pawl 370 and second pawl 400 from drive ring 270′ asdiscussed below. Pawl decoupling ramp 476 also functions as a stop tolimit the pivoting of operating lever 325 in the counterclockwisedirection.

The operation of shift assisting apparatus 14′ may be understood byreferring to FIGS. 5-12. FIG. 5 shows shift assisting apparatus 14′ in asteady-state idle condition. In this condition, control surface 454 ofoperating lever 325 supports first pawl control abutment 398 so thatfirst pawl tooth 382 is held radially outwardly in the first disengagedposition, and pawl decoupling ramp 480 supports second pawl controlabutment 428 so that second pawl tooth 412 is held radially outwardly inthe second disengaged position. Thus, drive ring 270′ rotates togetherwith axle 30 without having any effect on shift assisting apparatus 14′.

FIG. 6 shows what happens when operating wire 460 is pulled to the leftwhich, in this embodiment, causes the assisting apparatus 14′ to movetransmission actuating wire 340 in an upshifting direction. Pullingoperating wire 460 causes operating lever 325 to rotate clockwise, thusremoving control surface 454 from first pawl control abutment 398. As aresult, first leaf spring 388 causes first pawl 370 to rotate clockwise,thus moving first pawl tooth 382 radially inwardly into the firstengaged position. Consequently, when one of the abutments 292A or 292Bof drive ring 270′ (e.g., abutment 292A) rotates to the circumferentialposition of first pawl tooth 382, first pawl tooth 382 contacts theabutment, and cam member 304 rotates counterclockwise together withdrive ring 270′ and axle 30 to the position shown in FIG. 7. At thattime, second pawl control abutment 428 slides off of pawl decouplingramp 480, and second leaf spring 418 causes second pawl 400 to rotateclockwise so that second pawl tooth 412 moves radially inwardly into thesecond engaged position to contact the other one of the abutments 292Aor 292B (e.g., abutment 292B). Of course, it is not necessary for secondpawl tooth 412 to contact any abutment on drive ring 270′ as long as cammember 304 is able to rotate under the coupling force of first pawltooth 382.

Cam surface 308 has an increasing radius in the clockwise direction, soroller 334 on cam follower lever 312 moves radially outwardly, thuscausing transmission actuating element coupling member 316 to pulltransmission actuating wire 340. Counterclockwise rotation of cam member304 continues until cam surface 308 causes cam follower lever 312 tonearly complete the necessary amount of pulling of transmissionactuating wire 340 as shown in FIG. 8. At this time, first pawl controlabutment 398 is near pawl decoupling ramp 480 and second pawl controlabutment 428 is near pawl decoupling ramp 476.

As shown in FIG. 9, as cam member 304 continues to rotate, first pawlcontrol abutment 398 slides up pawl decoupling ramp 480 to move firstpawl tooth 382 radially outwardly toward the first disengaged position,and second pawl control abutment 428 slides up pawl decoupling ramp 476to move second pawl tooth 412 radially outwardly toward the seconddisengaged position. Thereafter, as shown in FIG. 10, cam member 304moves slightly until second pawl control abutment 428 is supported inthe second disengaged position by control surface 454 of operating lever325, and first pawl control abutment 398 is supported in the firstdisengaged position by pawl decoupling ramp 480. At that time, cammember 304 stops rotating, and transmission actuating wire 340 ismaintained in the upshifted position.

To release transmission actuating wire 340 back into the downshiftedposition, operating wire 460 is pulled once again as shown in FIG. 11.As a result, operating lever 325 again rotates clockwise, thus removingcontrol surface 454 from second pawl control abutment 428. Second pawl400 rotates clockwise in accordance with the biasing force of secondleaf spring 418, thus moving second pawl tooth 412 radially inwardlyinto the second engaged position. Thus, when one of the abutments 292Aor 292B of drive ring 270′ (e.g., abutment 292A) rotates to thecircumferential position of second pawl 400, second pawl tooth 412contacts the abutment, and cam member 304 rotates counterclockwisetogether with drive ring 270′ and axle 30 to the position shown in FIG.12. At the same time, first pawl control abutment 398 slides off of pawldecoupling ramp 480, and first pawl 370 rotates clockwise in accordancewith the biasing force of first leaf spring 388 so that first pawl tooth382 moves radially inwardly into the first engaged position to contactthe other one of the abutments 292A or 292B (e.g., abutment 292B).

The radius of cam surface 308 now quickly decreases in the clockwisedirection, so roller 334 on cam follower lever 312 moves radiallyinwardly, thus causing transmission actuating element coupling member316 to release transmission actuating wire 340.

Counterclockwise rotation of cam member 304 continues until assistingapparatus 14′ returns to the original position shown in FIG. 5. That is,first pawl control abutment 398 slides up pawl decoupling ramp 476 andis supported by control surface 454 of control lever 325 so that firstpawl tooth 382 is held in the first disengaged position. Likewise,second pawl control abutment 428 slides up pawl decoupling ramp 480 andis supported by pawl decoupling ramp 480 so that second pawl tooth 412is held in the second disengaged position.

It should be readily apparent that the embodiment shown in FIGS. 3-12operates by successive pulling of an operation wire in the samedirection to perform both an upshifting and a downshifting operation.FIG. 13 is an oblique view of a bicycle bottom bracket assembly 10 thatincorporates another embodiment of an assisting apparatus 514 accordingto the present invention for shifting a bicycle transmission. Thestructure of bottom bracket assembly 10 and crank arm assemblies 42 and46 is the same as in the embodiment shown in FIGS. 1 and 2, so adetailed description of those components shall be omitted. As discussedin more detail below, assisting apparatus 514 upshifts a frontderailleur 520 by moving an operating lever 524 clockwise and thendownshifts front derailleur 520 by moving operating lever 524counterclockwise. Operating lever 524 includes a wire coupling 525 forattachment to an operating wire 523 which, in turn, is connected to ashift operating device located at the handlebar (not shown).

In this embodiment, front derailleur 520 is integrally formed withassisting apparatus 514. More specifically, assisting apparatus 514includes a mounting member 526 that also functions as the base member offront derailleur 520. In all other respects front derailleur 520 has aconventional structure wherein a conventional linkage mechanism 528 isconnected between base (mounting) member 526 and a chain guide 532 sothat pulling and releasing an actuating arm 536 coupled to linkagemechanism 528 moves chain guide 532 laterally inwardly and outwardly tomove a chain (not shown) between large sprocket 136 and small sprocket144.

FIG. 14 is an oblique view of the assisting apparatus 514 with thederailleur 520 and crank arm assembly 46 removed. As with the firstembodiment, a drive ring 170′ is shown with a smooth inner peripheralsurface 171′, and it is shown attached to axle 30 in FIGS. 16-21 to helpunderstand the operation of the device. An arcuate operating lever 530has a first end pivotably connected to mounting member 526 through apivot shaft 534 which is also connected to operating arm 524 forpivoting around an operating lever axis W. A spring 535 is disposedaround pivot shaft 534 and is connected between mounting member 526 andoperating lever 530 for biasing operating lever 530 in thecounterclockwise direction. A first control projection 538 extendsradially inwardly from an intermediate portion of operating lever 530and terminates with a laterally inwardly extending first pawl controlledge 542 (FIG. 16) having a radially outwardly facing first pawlcontrol surface 544. Similarly, a second control projection 548 extendsradially inwardly from the second end of operating lever 530 andterminates with a laterally inwardly extending second pawl control ledge552 having a radially inwardly facing second pawl control surface 554.

FIGS. 15A and 15B show mounting member 526 in more detail. Mountingmember 526 includes a first ledge opening 562 for receiving first pawlcontrol ledge 542 therethrough, a second ledge opening 566 for receivingsecond pawl control ledge 552 therethrough, and a pawl control groove570 formed by a radially outwardly facing pawl control surface 574 and aradially inwardly facing pawl control surface 578. Pawl control surface574 has a generally circular shape except for a first control ledgepassage 582 for allowing radially inward movement of first control ledge542, a pawl decoupling ramp 586 and a pawl decoupling ramp 590.Similarly, pawl control surface 578 has a generally circular shapeexcept for a second control ledge passage 594 for allowing radiallyoutward movement of second control ledge 552, a pawl decoupling ramp 596and a pawl decoupling ramp 598. The functions of pawl decoupling ramps586, 590, 596 and 598 will be discussed below.

As shown in FIG. 16, a cam 604 having a cam surface 608 is mounted tomounting member 526 for rotation around the axis Y shown in FIG. 14. Acam follower 612 has the form of a two-piece lever (612A, 612B) whereina first end of lever piece 612A is pivotably mounted to mounting member526 through a pivot shaft 616 and a second end of lever piece 612Aincludes a roller 620 for engaging cam surface 608. Pivot shaft 616extends through the side of mounting member 526 and is coupled to afirst end of lever piece 612B. A second end of lever piece 612B containsa transmission actuating coupling member in the form of an opening 626for receiving a derailleur actuating wire 630 therethrough. Derailleuractuating wire 630 has a wire end bead 634 for preventing derailleuractuating wire 630 from being pulled upwardly out of opening 626.

As in the first embodiment, a first coupling member 654 is coupled forrotation of the cam member 604, wherein the first coupling member 654moves between a first engaged position and a first disengaged position;and a second coupling member 656 is coupled for rotation of the cammember 604, wherein the second coupling member 656 moves between asecond engaged position and a second disengaged position.

First coupling member 654 comprises a first pawl 670 and a first pawlmounting member 674. A first end of first pawl 670 is pivotablyconnected to first pawl mounting member 674 through a first pivot shaft678, and a second end of first pawl 670 has a radially inwardlyextending first pawl tooth 682 and a first pawl control abutment 684.First pawl mounting member 674 is fixed to cam member 604 by a screw686. A first biasing mechanism in the form of a first leaf spring 688has a first end 690 fixed to cam member 604 and a second end 694abutting against the second end of first pawl 670. First leaf spring 688biases first pawl tooth 682 radially inwardly to a first engagedposition wherein first pawl 670 engages either abutment 192A or 192B ondrive ring 170′ as discussed below.

Similarly, second coupling member 656 comprises a second pawl 700 and asecond pawl mounting member 704. An intermediate portion of second pawl700 is pivotably connected to second pawl mounting member 704 through asecond pivot shaft 708. A first end of second pawl 700 has a radiallyinwardly extending second pawl tooth 712, and a second end of secondpawl 700 has a second pawl control abutment 714. Second pawl mountingmember 704 is fixed to cam member 604 by a screw 716. A second biasingmechanism in the form of a second leaf spring 718 has a first end 722fixed to cam member 604 and a second end 724 abutting against the firstend of second pawl 700. Second leaf spring 718 biases second pawl tooth712 radially inwardly to a second engaged position wherein second pawl700 engages either abutment 192A or 192B on drive ring 170′ as discussedbelow.

The operation of shift assisting apparatus 514 may be understood byreferring to FIGS. 16-21. FIG. 16 shows shift assisting apparatus 514 ina steady-state idle condition. In this initial condition, first pawlcontrol surface 544 of first pawl control ledge 542 supports first pawlcontrol abutment 684 so that first pawl tooth 682 is held radiallyoutwardly in the first disengaged position, and pawl decoupling ramp 598presses second pawl control abutment 714 radially inwardly so thatsecond pawl tooth 712 is held radially outwardly in the seconddisengaged position. Thus, drive ring 170′ rotates together with axle 30without having any effect on shift assisting apparatus 514.

FIG. 17 shows what happens when operating wire 523 is pulled upwardly.In this case, operating levers 524 and 530 pivot clockwise around pivotshaft 534 against the biasing force of spring 535, and first pawlcontrol ledge 542 allows first pawl control abutment 684 to moveradially inwardly. As a result, first pawl 670 rotates counterclockwisein accordance with the biasing force of first leaf spring 688, thusmoving first pawl tooth 682 radially inwardly into the first engagedposition. Thus, when one of the abutments 192A or 192B of drive ring170′ (e.g., abutment 192A) rotates to the circumferential position offirst pawl 670, first pawl tooth 682 contacts the abutment, and cammember 604 rotates clockwise together with drive ring 170′ and axle 30to the position shown in FIG. 18. At the same time, second pawl controlabutment 714 slides off of pawl decoupling ramp 598, and second pawl 700rotates counterclockwise around pivot shaft 708 in accordance with thebiasing force of second leaf spring 718 so that second pawl tooth 712moves radially inwardly into the second engaged position to contact theother one of the abutments 192A or 192B (e.g., abutment 192B).

Cam surface 608 has an increasing radius in the counterclockwisedirection, so roller 620 on lever piece 612A moves radially outwardly,thus causing lever piece 612B to pull actuating wire 630 downwardly.Clockwise rotation of cam member 604 continues until cam surface 608causes cam follower 612 to nearly complete the necessary amount ofpulling of derailleur actuating wire 630 as shown in FIG. 18. At thistime, first pawl control abutment 684 is near pawl decoupling ramp 590and second pawl control abutment 714 slides up pawl decoupling ramp 596(rotating second pawl 700 clockwise), contacts the second pawl controlsurface 554 of second pawl control ledge 552 and disengages second pawltooth 712 from abutment 192B. Also, roller 620 on lever piece 612A isdisposed immediately counterclockwise of a cam ridge 730 on cam 604.

As shown in FIG. 19, as cam member 604 continues to rotate, first pawlcontrol abutment 684 slides up pawl decoupling ramp 590 so that firstpawl 670 rotates clockwise and moves first pawl tooth 682 into the firstdisengaged position. Also, second pawl control abutment 714 moves to theclockwise end of second pawl control surface 554. The radially inwardforce applied by roller 620 to cam ridge 730 ensures that cam member 604rotates slightly clockwise so that first pawl control abutment 684 isproperly positioned on pawl decoupling ramp 590 and first pawl tooth 682is disengaged from abutment 192A. At that time, cam member 604 stopsrotating and derailleur actuating wire 630 is maintained in theupshifted position.

To release actuating wire 630 to shift the bicycle transmission into thedownshifted position, operating wire 523 is released as shown in FIG.20. In this case, operating levers 524 and 530 pivot counterclockwisearound pivot shaft 534 in accordance with the biasing force of spring535, and second pawl control ledge 552 allows second pawl controlabutment 714 to move radially outwardly. As a result, second pawl 700rotates counterclockwise around pivot shaft 708 in accordance with thebiasing force of second leaf spring 718, thus moving second pawl tooth712 into the second engaged position. Thus, when one of the abutments192A or 192B of drive ring 170′ (e.g., abutment 192A) rotates to thecircumferential position of second pawl 700, second pawl tooth 712contacts the abutment, and cam member 604 rotates clockwise togetherwith drive ring 170′ and axle 30 to the position shown in FIG. 21. Atthe same time, first pawl control abutment 684 slides off of pawldecoupling ramp 590, and first pawl 670 rotates counterclockwise aroundpivot shaft 678 in accordance with the biasing force of first leafspring 688 so that first pawl tooth 682 moves radially inwardly into thefirst engaged position to contact the other one of the abutments 192A or192B (e.g., abutment 192B).

This portion of cam surface 608 contacting roller 620 has a decreasingradius in the counterclockwise direction as shown in FIG. 21, so roller620 on lever piece 612A moves radially inwardly, thus causing leverpiece 612B to release derailleur actuating wire 630. Clockwise rotationof cam member 604 continues until cam surface 608 causes cam follower612 to nearly complete the necessary amount of releasing of actuatingwire 630 as shown in FIG. 21. At this time, second pawl control abutment714 is near pawl decoupling ramp 598, and first pawl control abutment684 slides up pawl decoupling ramp 586 (thus rotating first pawl 670clockwise), contacts the first pawl control surface 544 of first pawlcontrol ledge 542 and disengages first pawl tooth 682 from abutment192B. Also, roller 620 on cam follower lever 612 is disposed immediatelycounterclockwise of a cam ridge 734 on cam 604.

As cam member 604 continues to rotate, second pawl control abutment 714slides up pawl decoupling ramp 598 so that second pawl 700 rotatesclockwise to move second pawl tooth 712 into the second disengagedposition, and first pawl control abutment 684 moves to the clockwise endof first pawl control surface 544. The radially inward force applied byroller 620 to cam ridge 734 ensures that cam member 604 continuesrotating until second pawl control abutment 714 is properly positionedon pawl decoupling ramp 598 and second pawl tooth 712 is disengaged fromabutment 192A. At that time, cam member 604 stops rotating, andactuating wire 630 is maintained in the upshifted position as shown bythe initial position in FIG. 16.

FIG. 22 is a partial cross sectional view of a bicycle bottom bracketassembly 10 that incorporates another embodiment of an assistingapparatus 14′ according to the present invention for shifting a bicycletransmission. This embodiment may use any of the structures otherwiseshown in FIGS. 1-22. The difference between this apparatus and thedevices shown in FIGS. 1-22 is primarily in the construction of a crankarm assembly 46″ similar but no identical to crank arm assembly 46′shown in FIG. 2B. Thus, the elements which are the same as the elementsin FIGS. 1 and 2B have the same reference numbers, and a detaileddescription of those elements shall be omitted.

In this embodiment, upshifting chain supporting elements 201A, 201B,201E and 201F are provided, and upshifting chain supporting elements201B and 201F are located approximately 57.55° clockwise of thelongitudinal median axis R of crank arm 120. Downshift facilitatingteeth 203X having chamfered side surfaces 203Y are provided immediatelyclockwise of chain receiving recesses 203Z located approximately 11.74°clockwise of the longitudinal median axis R of crank arm 120. As aresult of these structures and their orientation, a drive ring 170″ ismounted to a crank axle mounting boss 124″ with a specific orientation,wherein drive ring 170″ includes drive projections 190A′ and 190B′forming abutments 192A′ and 192B′.

As with the embodiment shown in FIG. 2B, abutments 192A′ and 192B′follow an imaginary straight line extending radially outwardly from theaxis of rotation X of crank arm assembly 46″ and perpendicular to anouter peripheral surface 123′ of crank axle mounting boss 124″. However,in this embodiment abutments 192A′ and 192B′ are located approximately75° clockwise of the longitudinal median axis R of crank arm body 120.This allows the abutments to time the operation of assist mechanism 14′so that the chain will be in the proper position to take maximumadvantage of upshifting chain supporting members 201A, 201B, 201E and201F and downshift chain facilitating teeth 203X.

As shown in FIGS. 23 and 24, drive ring 170″ has a smooth innerperipheral surface 171″ that is press-fit onto the outer peripheralsurface 123′ of a crank axle mounting boss 124″. Inner peripheralsurface 171″ includes arcuate recesses 172A and 172B that engagecorresponding arcuate projections 125A and 125B, respectively,positioned on the outer peripheral surface of 123′ of crank axlemounting boss 124′ to ensure that drive ring 170′ is fitted on crankaxle mounting boss 124″ so that abutments 192A′ and 192B′ will have theappropriate mounting angle. To accommodate arcuate recesses 172A and172B without compromising the strength of drive ring 170″ and to keepthe diameter of drive ring 170″ at a minimum, projections 190A′ and190B′ have thickened abutment-forming portions 193A and 193B,respectively, with generally flat top surfaces 194A and 194B. Arcuaterecesses 172A and 172B are disposed in these thickened abutment-formingportions 193A and 193B, respectively. Inclined surfaces 195A and 195Bextend radially inwardly from the clockwise ends of surfaces 194A and194B, respectively.

As shown in FIG. 22, drive ring 170″ also has a specific relationship tosmall diameter sprocket 144 and splines 98 in the direction of therotational axis X. In this embodiment, drive ring 170″ has a thicknessof 3.0 millimeters in the direction of rotational axis X. A plane Pcontaining an inner side 176A of drive ring 170″ is located 3.3millimeters from an inner side surface 145 of small diameter sprocket144. Thus, in this embodiment a plane Q containing the outer side 176Bof drive ring 170″ will be located approximately 0.3 millimeters formthe inner side surface 145 of small diameter sprocket 144. Plane P alsois located approximately 9.5 millimeters from the innermost ends 97 ofsplines 98. Preferably, plane P is located at least 5 millimeters fromthe innermost ends 97 of splines 98.

In this embodiment, the outer peripheral surface 123′ of crank axlemounting boss 124″ defines a seal supporting groove 126 and a sealsupporting ledge 127 for supporting an annular rubber seal 800. As shownmore specifically in FIG. 25, seal 800 has an annular base member 802,wherein base member 802 includes a radially inwardly projecting engagingprojection 804 for engaging seal supporting groove 126 and an engagingledge 808 for engaging seal supporting ledge 127. A lip seal 829 extendsradially outwardly from base member 802 for contacting a radiallyinwardly facing surface 137A of cover 137′. With this sealing structurethere is less chance that contaminants falling between crank armassembly 46″ will prematurely wear out the seal.

While the above is a description of various embodiments of the presentinvention, further modifications may be employed without departing fromthe spirit and scope of the present invention. For example, the driveprojections 190A and 190B also may be formed directly on the lateralside wall or the outer peripheral surface of the crank axle mountingbosses 124 or 224 and project laterally inwardly. The size, shape,location or orientation of the various components may be changed asdesired. The functions of one element may be performed by two, and viceversa. It is not necessary for all advantages to be present in aparticular embodiment at the same time. Every feature which is uniquefrom the prior art, alone or in combination with other features, alsoshould be considered a separate description of further inventions by theapplicant, including the structural and/or functional concepts embodiedby such feature(s). Thus, the scope of the invention should not belimited by the specific structures disclosed or the apparent initialfocus on a particular structure or feature.

1. A drive mechanism for a bicycle transmission assist mechanismcomprising: a crank arm having a crank axle mounting hole around arotational axis; a drive member supported coaxial with the rotationalaxis and including: a first abutment facing a forward rotationaldirection of the crank arm; and a first sloped surface extending from aradially outer portion of the abutment and facing a rearward rotationaldirection of the crank arm; wherein the drive member is not structuredto couple sprockets to the crank arm; and wherein an outer peripheralsurface of the drive member at a location of intersection with aradially inner portion of the first abutment extends at a substantiallyconstant radius of curvature for more than 20°.
 2. The drive mechanismaccording to claim 1 wherein the drive member further comprises: asecond abutment facing a forward rotational direction of the crank arm;and a second sloped surface extending from a radially outer portion ofthe abutment and facing a rearward rotational direction of the crankarm; and wherein the outer peripheral surface of the drive member at alocation of intersection with a radially inner portion of the secondabutment extends at a substantially constant radius of curvature formore than 20°.
 3. A drive mechanism for a bicycle transmission assistmechanism comprising: a bicycle crank arm having a crank axle mountingboss including a crank axle mounting hole and a rotational axis, whereinthe crank axle mounting boss protrudes axially; a drive member disposedat the crank axle mounting boss and including: an outer peripheralsurface; wherein an abutment is disposed on the outer peripheral surfaceand faces a forward rotational direction of the crank arm; wherein theabutment rotates around the rotational axis at a substantially constantradius; and wherein the outer peripheral surface at a location ofintersection with a radially inner portion of the abutment extendsconvex for at least 20°; and wherein the drive member is not structuredto couple sprockets to the crank arm.